Cell-cell interactions, and cell-drug interactions, will be studied with viable functioning cells. Monitoring of the reactions will be carried out with microcalorimeters which have been constructed for this kind of work. The consequences of varying techniques used in removing cells out of tissue, particularly in certain blood vessel intima, will be studied. The receptor sites on intima cells, particularly for biogenic amines, will be assayed. This will be done by following heat production, using glucose as a source of energy, controlled by the amine. Similar work will be carried out with oat coleoptile, with plant hormone controls. The effort will be aimed at using microcalorimetrc heat production as a means of screening for hormones, and other biologically active molecules. Collaborative work, with tumor tissue culture cells, and with frog egg nuclear transplant thermogenesis, will be done.